Interlocking system for railroads



M M E Sept. 22, 1931. w. K. HOWE INTERLOCKING SYSTEM FOR RAILROADS 4llllllll Ill o I! lI/t lllllll e mm M n a Q m EH 5 0m O o ,beenaccomplished by Patented Sept. 22, 1931 UNITED STATES PATENT FriesWINTHRO]? K. HOWE, OF ROCHESTER, NEW YCRK, ASSZGNO R TO GENERAL RAILWAYSIGNAL COMPANY, OF ROCHESTER, NEW YORK INTERLOGKING SYSTEM FOR RAILROADSApplication filed November 14, 1929.

This invention relates to interlocking systems for railroads, and moreparticularly pertains to indication means and devices for use in suchinterlocking systems.

Where a number of track switches are controlled by their respectivecontrol levers located in a central tower, it is desirable to providemeans indicating in the tower the position and locked condition of theassociated track switches, so that the governing control levers may beallowedto be operated to full normal or full reverse positions only whenthe associated switch machines are in corresponding normal, or reversepositions and locked. In one type of system, this has the use ofseparate line wires comprising a polarized circuit controlled by thetrack switch for operating a three position SS, or switch repeating,relay in the interlocking tower.

In accordance with the present invention, it is proposed to provide suchan SS relay which is controlled over the regular operat ing wires of theswitch machine by the use oi super-imposed alternating current. Morespecifically, it is proposed to employ the two field windings, of adouble field winding type electric motor, alternately as the primary andsecondary windings of a transforming means for super-'mposingalternating current upon the control wires of said electric motor.further object is to so correlate the indication system with the controlsystenithat it will be impossible for the control lever to be operatedout of correspondence with its switch machine.

Other objects, characteristic features and advantages of the presentinvention will be in part obvious from the accompanying drawing, and inpart pointed out as the description of the invention progresses.

The single figure of the accompanying drawing represents in adiagrammatic manner one embodiment of the present invention as appliedto one type of electric interlocking system.

'With reference to the accompanying drawing, one end of a passing sidingPS has been shown with a track switch TS connecting it to a stretch ofmain track MT. The main A i when the track switch operation. The movablecontact 6 makes conintermediate position.

Serial No. 40?,133.

track MT, and the portion of the siding out to the fouling point areprovided with inture A and two field windings F and F one of which, whenenergized in series with the armature, operates the switch machine inone direction; and the other of which, when energized in series with thearmature,

operates the switch machine in an opposite direction. Included in theswitch machine control circuit is a brake BR which normally preventsoperation of the switch machine except when a normal value of operatingcurrent is flowing in its windings to actuate it .to a releasedcondition. Associated with the rack switch TS and switch machine SM aremovable contacts 6, 7 and 8 which assume extreme normal orreversepositions when the track switch TS is in extreme normal or reversepositions respectively and locked, and which assumeintermediate centralpositions TS is unlocked or in tact between a pair of fixed contactswhen in a normal or interinediate'position, while the movable contact 7makes contact between a pair of'iixed contacts when in a reverse or Themovable contact 8 makes contact between one pair of fixed contacts whenin a normal position and another pair of fixed contacts when in areverse position. 1

A transformer T has its primary connected to a suitable alternatingcurrent source of potential provided bya transmission line extendingfrom the interlocking tower, and has its secondary provided with acenter tap for purposes hereinafter set forth;

. In the interlocking tower, a control lever L is provided forcontrolling the switch machine SM- over normal and reverse operatingwires 9 and 10 respectively. The lever L operates movable contact blocks11, 12 and 13 to which it is connected by a suitable rod. These movablecontact blocks 11, 12 and 13 make contact between certain pairs of fixedcontacts when the control lever L is in normal or half normal positionsN and HN respectively, and make contact between certain other standpointof operation.

tions of a protective relay and low reslstance ,windlngs pairs of fixedcontacts when the control lever L is in reverse or half reversepositions R and HR respectively. The lever Lv is prevented from movementto the full normal or the full reverse position by the usual indicationlatch mechanism IL which is released by the energization of anindication magnet IM. A safety magnet S is provided which, whenenergized, prevents the actuation of the indication latch mechanism ILby the indication magnet IM. 1

The lever L is provided with a lever latch 14 which operates an energysaving contact 15, Also, a tappet bar Q0 is operated by a cam slot inthe lever L in the usual manner for controlling the mechanicalinterlocking between the lever L and its associated opposing levers. I

A SS relay is provided with a local winding 16 continuously energizedfrom the secondary of a local transformer T the primary of whichisconnected to the same transmission line as the local transformer T atthe switch machine. The line phase winding 17 of the SS relay isenergized by alternating current supplied from the local transformer Tover the operating wires of the switch machine in a manner ashereinafter set forth. 'The contact 18 of'the SS relay is operated to anextreme normal or reverse position depending upon the instantaneousrelatlve polarity of the alternating currentin the line phase winding17, and assumes a. central deenergized non-contacting position wheneither or both the local and line phase windings are deenergized.

A suitable power supply for the switch machine SM is provided by abattery BT, or any other convenient source of electrical potential.Operating current is supplied to the switch machine SM in accordancewith the position of the control lever L, the positions of a trackrepeating relay H and L respectlvely. The operating current of theswitch machine flows through normal and reverse operatlng c01ls of anindication selector IS to insure the correspondence of the lever L withthe switch TS.

It is believed that the usefulness of the system and the correlatedfunctions of the various devices will be best understood by further Idescription being given from the control TR, and the posi- PR having.high Operation of the system The track switch TS is shown in the normallocked position so that traffic may pass in either direction .over themain track MT. Also, the lever L in the interlocking tower is in a fullnormal position N controlling the tappet bar 20 to release certainconflicting levers by the mechanical interlocking between levers in theusual well known manner.

Assuming that a contact 21 of the indication selector IS is operated toa normal position by the last operation of the switch machine, thenormal energizing current for the line phase windings 17 of the SS relayis completed,.so that it receives energy from the transformer T Thisnormal energizing circuit for the SS relay is effective because thetransformer T energizes the field winding F which causes the fieldwinding F to act as the secondary of a transformer in which a current isinduced that energizes the line phase winding 17 of the relay SS overtlfie next operating circuit of the switch mac me.

circuit traced as follows :from the center tap of the secondary oftransformer T through wires 25 and 26, field winding F wire 27, contacts8-28, wire 29, to the right-handwires 30, and 31, armature A, wire 32,wind- .lng of brake BR, common wire C, wire 33,

back contact 34 of phase winding 37, contacts 1238, reverse operatingwire 10, contacts 639, wire 40, to the left-hand terminal of fieldwinding F With the line phase winding 17 of the relay SS energized overits normal energizing circuit, its instantaneous relative polarity issuch in relation with the instantaneous relative polarity of the localphase winding 16, that thecontact 18 assumes a right-hand normalenergized position, in which. position the energizing circuit of theindication magnet IM may be completed by actuation of the lever latch 14to close power saving contact 15.

Assuming the leverlatch 14 to be actuated, the normal energizing circuitfor the indication magnet IM is traced as follows :from the positiveterminal of a suitable source of electrical potential indicated as Bthrough contact 18 of relay SS in a right-hand normal position, wire 44,contacts 11 45, wire 46, contact 21 of indication selector IS in arightrelay PR, wire 35, line hand position, wire 47, windings ofindication magnet IM, wire 48, contact 15 in a 17 of relay SS, wires 36and 1 The field winding F 1s energized through a closed position, to thenegative terminal of the suitable source indicated as B The operator cancontrol the track switch TS to a reverse eXtreme position by themovement of the lever L 1n a left-hand direction until the half reverseposition HR is reached. Further movement is prevented by the indicationlatch mechanism IL until the indication magnet TM is again actuated.With the control lever L in a half reverse position, the initial reverseoper ting circuit for the switch machine is traced as follows :-from thepositive terminal of battery BT, through the fuse F wire 49, frontcontact 50 of relay TR, wire 51, high resistance windings H of relay PR,wires 52 and 53, low resistance winding L of relay PR, wire 54, windingsof safety magnet S, wires 55 and 56, reverse winding 57 ofindicationselector IS, wire 62, contacts 13-58, wire 59, reverseoperating wire 10, contacts 6-39, wire 40, field winding wires 30 and31, armature A, wire 32, winding of brake BR, common wire C, to thenegative terminal of battery ET. This circuit, however, includes thehigh resistance winding H of relay PR which prevents sufficient currentfrom flowing in this circuit to operate the switch machine SM and theindication selector IS. However, the energization of the high resistancewinding H actuates the contacts of the relay PR to energized positions,one of which is then effective to shunt out the high resistance windingH allowing the operating currenoto reach a value suflicient to operatethe contact 21 of the indication selector TS to a left-hand extremeposition, suificient to release the brake BR of the switch machine, andsufficient to operate the switch machine SM. This shunt includes wire 60connected to fuse F front contact 61 of relay PR, the wire 53 and thelow resistance winding L. Thus, the contacts of the relay PR aremaintained in an actuated position by the energizat-ion of the lowresistance winding L although the high resistance winding H is shuntedout.

The switch machine SM now unlocks the track switch TS and operates it toa reverse position in which it is again locked.

During the operation of the switch machine SM and as soon as the trackswitch is unlocked, the movable contacts 6, 7 and 8 are operated totheir intermediate positions. With the contacts 6 and 7 in intermediatepositions both the reverse and normal energizing circuits are completedat the switch machine, thus the reverse energizing circuit is completedif the lever L is maintained in a reverse position, while the normalenergizing circuit will be completed if the lever L is returned to anormal position. With the movable contact 8 in an intermediate position,the energizing circuit for causing the field winding F to act as theprimary of a transformer is open at contacts 8-28, thus insuringdeenergization of the line phase winding 17 of the relay SS while thetrack switch is unlocked. It will be pointed out in this connection,that the line phase winding 17 is deenergized as soon as the contact 34of relay PR is actuated to an energized position even before the switchmachine SM receives operating current to unlock the track switch TS. I

As soon as the pletes the operation of the track switch TS to a reverseposition and locked condition, the contacts 6, 7 and 8 are operated totheir reverse eXtreme positions which causes the reverse operatingcircuit to be opened at contacts 6-39 and which causes alternatingcurrent potential to be placed across the field winding F so that itwill operate as the primary of a transformer in a similar manner as thefield winding F chine is in a normalposition. A predetermined time afterthe operating current of the switch machine ceases to flow through thelow resistance winding L of the relay PR, the

tions so that the energizing circuit for the l1ne phase winding 17 ofrelay SS may be completed.

lVith the switch machine SM in a reverse the field winding F isenergized position, from the transformer T through a circuit traced asfollows z-froin the center tap of the secondary of transformer T throughwires 25 and 30, field winding F wire 65, contacts left-hand terminal of8-66, wire 67, tothe the secondary of transformer T The field winding Fnow acts as the secondary of a transformer with its induced currentflowing through the reverse energizing circuit for the line phasewinding 17 of the SS relay, which circuit is traced as follows i-fromthe righthand terminal of field winding F through wires 26 and 31,armature A, wire 32, winding of brake BR, common wire C, wire 33, backcontact 34 of relay PR, wire 35, line phase winding 17 of relay SS, wire36, contacts 12-68, wires 69 and 9, contacts 7-70, wire 71, to theleft-hand terminal of field winding F As the reverse energizing circuitfor line phase winding 17 gives a current of reversed instantaneouspolarity, the contact 18 is now actuated from a deenergized position toa left-hand reverse position. may actuate the lever latch 14 whichcloses the contact 15 and thus energizes the indication magnet IMthrough a circuit traced as follows :-from the positive terminal of asuitable source of electrical potential indiwire 73, contacts 11-74,wire 75, contact 21 of indica ion selector TS in a left-hand reverseposition, wire 47 windings of indication magnet IM, wire 48, contact 15witch machine SM. comwhen the switch ma- The operator.

. 0 contacts 34 and 61 assume deenergized pos1- -5 cated as 13+, throughcontact 18 in a leftin hand position,

in a closed position, to the negative terminal the movable contacts ofof the suitable source indicated as B. The energization of theindication magnet IM releases the indication latch IL which permits theoperator to move the lever L further in a left-hand direction to thefull reverse position N which operates the tappet bar 20 in the usualmanner to release the mechanical interlocking between the lever L andcertain conflicting levers.

The operation of the system has been described from the normal conditionto' the reverse condition which is deemed sufiicient to point out thecharacteristic features of the present invention as the operation of thesystem from a reverse condition to normal con dition is merely aninverse function of the operation already described.

It will be noted that the relay PR allows its contacts 34 and 61 toassume biased deenergized positions a predetermined time after theoperating current of the switch machine SM ceases to flow in the lowresistance winding L. This releasing time period of the relay PR is ofsufiicient value to allow the control lever L to be moved from a halfnormal position I-IN to the half reverse position HR in mid-operation ofthe switch machine without the contact 61 opening its'front contact,which maintains the operating circuits intact for quick reversal.

The combination of the high resistance Winding II with the lowresistance winding L and the track repeater relay TR allows the switchmachine SM to complete its operation should a train enter the detectortrack section DT shortly after the track switch TS has begun to beoperated which, for example, is completely set forth in my pendingapplication Ser. No. 370,906 filed June 14, 1929.

From the above description, it is obvious that the control lever Lcannot be moved from a governing position such-as HR and HN to thecorresponding full positions R and N, due to the indication latchmechanism IL, except after said mechanism has been actuated b theenergization of the indication magnet IM. This indication magnet IMdepends for its energization upon the correspondence of the contact 21of the indication selector IS and thecontrol lever L with the positionassumed by the contact 18 of the SS relay. The SS relay in turn dependsupon the deenergization of the protective relay PR.

lVith such an arrangement, the control lever L cannot be moved to a newgoverning position and then returned to the former governing position toreceive an indication before the switch machine has operated to unlockthe track switch TS, which would be extremely undesirable should a fuseblow at that time allowing the momentum of the switch machine tocontinue to operate the track switch to an unlocked condition. Onemethod used to accomplish this result and the associated control leverthe circumstances in which such undesirable inent invention providesdouble check against such improper operation by the provision of theprotective relay PR and the indication selector IS.

The protective relay PR opens the energizing circuit for the line phasewinding of the SS relay before operating current for the switch machineflows and does not again close its back contact until after apredetermined time, which, as well as being sufficient to allow thecontrol lever L to be returned to a former governing position inmid-stroke ithout opening the control circuit, is also of suficientduration to permit the switch machine to come to rest should it havereceived any operating current when lever L was in the new governingposition. If the SS relay then indicates that the switch machine isstill in a locked extreme position in correspondence with the formergoverning position of the control lever L, indication magnet IM could beenergized and the control lever L be returned to a former full position.However, the indication selector IS prevents such returning'of thecontrol lever L in a manner as obvious from the above description if theswitch machine SM receives sufficient amount of operating current toaffect its operation.

However, if therequirements of practice demand that the control lever Lbe returned to a former full position although it has re-'' ceivedoperating current but has not unlocked the track switch, the indicationselector IS may be omitted without detracting from the presentinvention, as the protective relay PR is suflicient to meet the otherrequirements 4 of an interlocking system. The indication selector ISthus provides a double check that the control lever is in correspondencewith its switch machine and also an additional function as heretoforementioned, which is desirable in some cases.

An interlocking system has thus been shown and described which employsthe two field windings of an electric motor to act alternately as theprimary and secondary respectivelyofa transformer forsuper-imposingalternating current upon the control wires of theinterlocking system to accomplish the indication of the position andlocked condition ing tower, in a simple and economical manner, and alsoin a manner which prevents its to be moved out of correspondencetherewitl.

Having described one specific embodiment of the present invention, it isto be understood the various circuits'und devices are used ilitate inthe disclosure of the invention rather than to limit the invention toone s )8- l of a track switch in the interlock-' be understood thatvarious modifications, alterations and adaptations may be made to meetthe requirements of practice without departing from the spirit and scopeof the invention as set forth in the appended claims.

Having described my invention, I now claim 1. In an interlocking systemfor railroads, a track switch, a power operated switch machine having anelectric motor of the double field winding type, a control lever, normaland reverse operating wires governed by said control lever, contactsoperated jointly by said track switch and said switch machine forconnecting either said normal wire or said reverse wire to itsrespective one of said field windings to produce rotation in a directionto operate said track switch to an opposite position, means energizingthe last used field winding with alternating current, wherebyalternating current is induced in the other field winding connected bysaid contacts to its respective operating wire, and indication meanscontrolled by said induced currents.

2. In an interlocking system for railroads, a track switch, a poweroperated switch machine having an electric motor of the double fieldwinding type, one field for producing rotation in one direction and theother field for producing rotation in an opposite direction, and meansfor alternately using said field windings as primaryand secondarywindings of a transforming means in accordance with the position of saidtrack switch.

3. In an interlocking system for railroads, a. track switch, a poweroperated switch machine having an electric motor of the double fieldwinding type, means for alternately energizing one or the other of saidfield windings with alternating current in accordance with the positionof said track switch, whereby alternating current is induced in theopposite field winding, and indication means operated by said inducedcurrent with sald indication means indicating the position of said trackswitch.

4. In an electric motor for railroad signaling purposes, an armature, afield winding having a center tap connected to said armature, operatingcircuits connected to the extremities of said field winding and to theopposite terminal of said armature, and means energizing one-half ofsaid field winding with alternating current to induce a current forindication purposes in the operating circuit connected to the other halfof said field winding.

5. In an interlocking system for railroads, a track switch, a switchmachine, a control lever, normal and reverse operating circuits, anindication latch mechanism, means indicating the position and lockedcondition of said track switch for governing said indication latchmechanism, means connecting said indicating means across said operatingcircuits, means for super-imposing alternating current upon saidoperating circuits, and means for disconnecting said indication meansfrom said operating circuits when said switch machine receives operatingcurrent.

6. In an interlocking system for railroads of the type substantially asshown and described, a track switch, a switch machine driven by a motorhaving two field windings, a control lever, operating circuits,indication means, and means including said field windings forsuper-imposing alternating current on said operating circuits forcontrolling said indication means.

7. In an interlocking system for railroads, a track switch, a poweroperated switch machine having an electric motor of the double fieldwinding type, normal and reverse operating wires, contacts operated bysaid track switch and said switch machine for connecting either saidnormal wire or saidreverse wire to its respective field winding depending upon the position of said track switch, a common wire, meansenergizing one of said operating wires and said common wire to operatesaid track switch to one position or the other, a shunt cross protectioncircuit, indication means included in said shunt cross protectioncircuit, means opening said shunt cross protection circuit duringoperation of said switch machine, and means energizing said indicationmeans with alternating current induced in the one of said field windingsconnected to its operating wire while said switch machine is at rest.

8. In an interlocking system for railroads, a track switch, a poweroperated switch machine having a double field winding type elec-. tricmotor, means for alternately energizing one or the other of said fieldwindings with alternating current of opposite relative polarityrespectively in accordance with the position of said track switch,whereby alternating current is induced in the opposite field winding,and indication means responsive to said induced alternating current andresponsive to the change of relative polarity of said inducedalternating current, with said indication means giving indication of theposition and locked condition of said track switch.

9. In an interlocking system for railroads, a track switch, a switchmachine having normal and reverse operating circuits, a control lever,an indication latch mechanism, indication means indicating' the positionand locked condition of said track switch, said means having controlcircuits in part including said switch machine operating circuits, meansfor super-imposing alternating current upon said control. circuits ofsaid indication means, and means actively disconnecting said controlcircuits of said indication means from said operating circuits when saidswitch machine receives operating current, said means maintaining itsactive condition for a predetermined time after said operating currentof said switch machine ceases to flow.

10. In an interlocking system for railroads, atrack switch, a poweroperated switch machine having an electric motor of the double fieldwinding type, normal and reverse operating wires, contacts operated bysaid track switch and said switch machine connecting either said normal'or said reverse wire to its respective field winding depending upon theposition of said track switch, a common wire, a control lever forenergizing one or the other of said operating wires and said commonreturn wire to operate said track switch to one position or another, anindication selector having a contact operated to one position or anotherin accordance whether operating current flows in said normal or saidreverse operating wire, an indication latch mechanism, indication meanshaving an indication circuit in part including said normal or reverseoperating wire and said common wire, means energizing said indicationmeans with alternating current of opposite relative instantaneouspolarity according to the position of said track switch, means foropening said indication circuit of said indica'lion means duringoperation of said switch machine, and means for actuating saidindication latch mechanism when said control lever and saidindicationselector are in correspondence with the indication given .by saidindication means.

11. In an interlocking system for railroads; a track switch, a poweroperated switch machine having a double field winding type electricmotor, means for alternately energizing one or the other of said fieldwindings with alternating current of opposite instantaneous relativepolarity respec tively in accordance with the position of said trackswitch, said means including a transformer having a center tap, wherebyalternating current is induced in the opposite field winding, andindication means responsive to said induced alternating current andresponsive to the change of instantaneous relative polarity of saidinduced alternating current, said indication means giving indication inaccordance therewith of' the position and locked condition of said trackswitch.

12. In combination, a motor having an armature and field windings,normal and reverse operating circuits for said motor, and meansincluding said field windings for superimposing a current of distinctivecharacter upon said opera-ting circuits.

13. In combination,v a motor having field windings, normaland reverseoperating circuits for said motor, indication means, normal and reverseindication circuits for said indication means, sa1d indication circuitsincluding in part said reverse and normal operating circuitsrespectively, and means ineluding said field windings for inducing a'current of distinctive character in said indication circuits.

14. In combination, erable to normal and electric motor for operatingsaid switch machine, said motor having field windings, operatingcircuits for said motor, indication means responsive to currents ofdistinctive character, indication circuits for said indication means,and means including said field windings for energizing said indicationcir-. cuits with currents of distinctive character depending upon theposition of said switch machine.

15. In combination with a railroad switch machine, an electric motorhaving field windings, a control lever operable to normal and reversepositions, two control wires each used separately in a circuit with acommon return wire for operatingsaid motor in opposite directions eachcircuit of which is established so long said lever and'said switchmachine are out of correspondence, an indicating relay associated withsaid lever, two indicating circuits for said indicating relay each ineluding a difierent control wire together with said common return wireand completed only when said lever and said switch machine are incorrespondence, and means including said field windings for causing aflow of current in saidindication circuits respectively in accordancewith the position of said switch machine.

In testimony whereof I afiix my signature.

WVINTHROP K. HOIVE.

a switch machine opreverse positions, an

